(1) Field of the Invention
The present invention relates to an epoxy resin composition. More particularly, the present invention relates to an epoxy resin composition which has a very small molding shrinkage and an excellent precision moldability and can be valuably used as a sealing material for a semiconductor.
(2) Description of the Related Art
Since an epoxy resin is excellent in the bonding strength, chemical resistance, mechanical strength and electrically insulating property, the epoxy resin is widely used as an adhesive, a coating material, a cast product and a molded article. Especially, the molded article is widely applied to an electrical part or electronic part while the excellent electrically insulating property is effectively utilized. As an example of this application, there can be mentioned an epoxy resin composition to be used for sealing a semiconductor. For instance, Japanese Unexamined Patent Publication No. 61-268750 discloses a composition comprising a phenol-curable epoxy resin and a mixed quartz filler comprising 1 to 80% by weight of spherical quartz powder having an average particle size of 1 to 25 .mu.m and 20 to 99% by weight of pulverized quartz powder. This composition is conveniently used for sealing a semiconductor because the flowability is good at the step of forming a semiconductor, the thermal expansion coefficient is small and the cracking resistance is high. Japanese Unexamined Patent Publication No. 61-83615 discloses a composition for use in attaining the same object, which comprises a cresol-novolak type epoxy resin and a phenol-novolak curing agent at an epoxy resin/curing agent equivalent ratio of from 1.1 to 1.5, and pulverized or spherical silica having an average particle size of up to 15 .mu.m and a maximum particle size of up to 100 .mu.m. Also this composition has excellent cracking resistance and moisture resistance, and a product having a low stress can be obtained by deviating the epoxy resin/curing agent equivalent ratio from the normal equivalent ratio. It is taught that this composition is therefore used for sealing a semiconductor.
In the epoxy resin to be used for an electrical or electronic part, by incorporating silica and appropriately adjusting the particle size and the like, trials have been made to obtain a composition capable of providing desired properties.
With recent development of the electronic technique and the like, appearance of a molded article having a very high dimension precision is desired, and this desire is not satisfied only by the selection of the kind and particle size of silica.
Since the epoxy resin has such a characteristic property that the stability becomes poor at about 100.degree. C., only press molding or transfer molding is applicable as the molding method, and the preparation of a precise molded article by injection molding is impossible and the productivity of the molded article is low. Moreover, even if a composition having a small molding precision is developed, the composition can hardly be applied to the production of a precision-molded article.